Defect free germanium oxide gap fill

ABSTRACT

Methods for forming defect-free gap fill materials comprising germanium oxide are disclosed. In some embodiments, the gap fill material is deposited by exposing a substrate surface to a germane precursor and an oxidant simultaneously. The germane precursor may be flowed intermittently. The substrate may also be exposed to a second oxidant to increase the relative concentration of oxygen within the gap fill material. A process for removal of germanium oxide is also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. patent application Ser.No. 17/119,648, filed Dec. 11, 2020, the entire disclosure of which ishereby incorporated by reference herein.

TECHNICAL FIELD

Embodiments of the disclosure generally relate to methods for forminggermanium oxide materials. In particular, embodiment of disclosurerelate to methods for forming defect free germanium oxide gap fill.

BACKGROUND

Germanium oxide is an increasingly important material in semiconductormanufacturing. Germanium is group 14 element, like silicon, and sogermanium containing materials often have similar properties as theirsilicon based analogs. Given the prevalence of silicon oxide insemiconductor manufacturing, there is an increased interest in germaniumoxide, its properties and methods for forming germanium oxide materialsin various processing schemes.

One scheme of interest is filling substrate features (e.g., vias,trenches, etc.) with gapfill material. Unfortunately, typical gapfillmethods often result in gap fill materials which contain defectsincluding seams and voids. The defects can cause multiple issues duringdownstream processing. The issues are often evidenced most clearly byetch processes which impact the defects differently than the surroundinggap fill. These defects can also cause deterioration of thepattern/device which contains the gap fill over time.

Accordingly, there is a need for novel methods of depositing gap fillwhich do not produce seams, voids or other defects within the depositedmaterials.

SUMMARY

One or more embodiments of the disclosure are directed to a method fordepositing a gap fill material. The method comprises exposing asubstrate surface comprising at least one feature to a germane precursorand a first oxidant to deposit a gap fill material comprising germaniumoxide within the at least one feature. The at least one feature has anopening width and extends a depth into the substrate. The gap fillmaterial has substantially no voids nor seam.

Additional embodiments of the disclosure are directed to a method fordepositing a gap fill material. The method comprises exposing asubstrate surface comprising at least one feature to a constant flow ofa first oxidant and an alternating flow of a germane precursor and asecond oxidant to deposit a gap fill material comprising germanium oxidewithin the at least one feature. The at least one feature has an openingwidth and extends a depth into the substrate. The germane precursor andthe second oxidant each have a duty cycle of less than or equal to 25%.The gap fill material has substantially no voids nor seam.

Further embodiments of the disclosure are directed to a method ofselectively removing germanium oxide. The method comprises exposing agermanium oxide layer to a basic aqueous solution.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentdisclosure can be understood in detail, a more particular description ofthe disclosure, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this disclosure and are therefore not to beconsidered limiting of its scope, for the disclosure may admit to otherequally effective embodiments.

FIG. 1 illustrates an exemplary substrate with a feature beforeprocessing according to one or more embodiment of the disclosure;

FIG. 2 illustrates an exemplary substrate after processing to form agapfill material according to one or more embodiment of the disclosure;and

FIG. 3 illustrates an exemplary substrate after processing to form asuper-conformal film according to one or more embodiment of thedisclosure.

DETAILED DESCRIPTION

Before describing several exemplary embodiments of the disclosure, it isto be understood that the disclosure is not limited to the details ofconstruction or process steps set forth in the following description.The disclosure is capable of other embodiments and of being practiced orbeing carried out in various ways.

As used in this specification and the appended claims, the term“substrate” refers to a surface, or portion of a surface, upon which aprocess acts. It will also be understood by those skilled in the artthat reference to a substrate can also refer to only a portion of thesubstrate, unless the context clearly indicates otherwise. Additionally,reference to depositing on a substrate can mean both a bare substrateand a substrate with one or more films or features deposited or formedthereon

A “substrate” as used herein, refers to any substrate or materialsurface formed on a substrate upon which film processing is performedduring a fabrication process. For example, a substrate surface on whichprocessing can be performed include materials such as silicon, siliconoxide, strained silicon, silicon on insulator (SOI), carbon dopedsilicon oxides, amorphous silicon, doped silicon, germanium, galliumarsenide, glass, sapphire, and any other materials such as metals, metalnitrides, metal alloys, and other conductive materials, depending on theapplication. Substrates include, without limitation, semiconductorwafers. Substrates may be exposed to a pretreatment process to polish,etch, reduce, oxidize, hydroxylate, anneal, UV cure, e-beam cure and/orbake the substrate surface. In addition to film processing directly onthe surface of the substrate itself, in the present disclosure, any ofthe film processing steps disclosed may also be performed on anunderlayer formed on the substrate as disclosed in more detail below,and the term “substrate surface” is intended to include such underlayeras the context indicates. Thus for example, where a film/layer orpartial film/layer has been deposited onto a substrate surface, theexposed surface of the newly deposited film/layer becomes the substratesurface.

FIG. 1 shows a cross-sectional view of a substrate 100 with a feature110. The disclosure relates to substrates and substrate surfaces whichcomprise at least one feature. FIG. 1 shows a substrate 100 having asingle feature 110 for illustrative purposes; however, those skilled inthe art will understand that there can be more than one feature. Theshape of the feature 110 can be any suitable shape including, but notlimited to, trenches, cylindrical vias, or rectangular vias.

As used in this regard, the term “feature” means any intentional surfaceirregularity. Suitable examples of features include, but are not limitedto trenches which have a top, two sidewalls and a bottom, and peakswhich have a top and two sidewalls without a bottom. Features can haveany suitable aspect ratio (ratio of the depth of the feature to thewidth of the feature) as discussed below.

The substrate 100 has a substrate surface 120. The at least one feature110 forms an opening in the substrate surface 120. The feature 110extends from the substrate surface 120 (also referred to as the topsurface) to a depth D to a bottom surface 112. The feature 110 has afirst sidewall 114 and a second sidewall 116. While the feature shown inFIG. 1 has parallel sidewalls 114, 116, the width of the feature is mostoften defined by the width W of the feature at the top opening of thefeature 110; this measurement may also be referred to as the openingwidth. The open area formed by the sidewalls 114, 116 and bottom 112 arealso referred to as a gap.

One or more embodiment of the disclosure is directed to methods fordepositing a gap fill material with substantially no defects. Someembodiments of the disclosure deposit a gapfill material withsubstantially no seam(s). Some embodiments of the disclosure deposit agapfill material with substantially no void(s). Some embodiments of thedisclosure advantageously deposit the gap fill material without plasma.Some embodiments of the disclosure advantageously deposit the gap fillmaterial without the use of a separate densification step.

One or more embodiment of the disclosure is directed to methods fordepositing a super-conformal film. Some embodiments of the disclosuredeposit a super-conformal film with a greater thickness on the sidewalland/or bottom than on the top surface. Some embodiments of thedisclosure advantageously deposit the super-conformal film withoutplasma. Some embodiments of the disclosure advantageously deposit thesuper-conformal film without the use of a separate etch process.

Referring to FIG. 2 , some embodiments of the disclosure relate tomethods for depositing a gap fill material 210 within a feature 110 of asubstrate 100. In some embodiments, the gap fill material 210 issubstantially free of defects, including, but not limited to seams andvoids. In some embodiments, the gap fill material 210 is substantiallyfree of seams. In some embodiments, the gap fill material 210 issubstantially free of voids.

As used in this specification and the appended claims, a seam is a gapor fissure that forms in the feature between, but not necessarily in themiddle of, the sidewalls of the feature 110. Without being bound bytheory, a seam may be formed when the lattice structures of films whichhave grown from the sidewalls of the feature do not harmonize as theymeet near the center of the feature.

As used in this specification and the appended claims, a void is avacant area in which the gap fill material 210 has not deposited withinthe feature 110. Without being bound by theory, voids often form whenmaterial deposits faster near the top of a feature and pinches closedthe opening of the feature before the gap fill material can completelyfill the feature. The remaining unfilled space is a void.

As used in this regard, the term “substantially free of seams” or“substantially free of voids” means that any crystalline irregularity orenclosed space without material formed in the space between thesidewalls of a feature is less than about 1% of the cross-sectional areaof the feature.

Referring to FIG. 3 , some embodiments of the disclosure relate todepositing a super-conformal film 310 within a feature 110 of asubstrate 100. The super-conformal film 310 has a sidewall thickness Tson the sidewalls 114, 116 and/or bottom thickness TB on the bottomsurface 112 that is greater than the top thickness TT on the substratesurface 120 outside of the feature 110. In some embodiments, the ratiobetween Ts and TT is greater than or equal to 1.2, greater than or equalto 1.5, greater than or equal to 2, greater than or equal to 3, orgreater than or equal to 4. In some embodiments, the ratio between TBand TT is greater than or equal to 1.2, greater than or equal to 1.5,greater than or equal to 2, greater than or equal to 3, or greater thanor equal to 4.

The methods for depositing the gap fill material 210 comprise exposingthe substrate 100 and the substrate surface 120, including at least onefeature 110, to a germane precursor and a first oxidant to deposit thegap fill material 210 within the feature 110. The gap fill material 210comprises germanium oxide.

The methods for depositing the super-conformal film 310 compriseexposing the substrate 100 and the substrate surface 120, including atleast one feature 110, to a germane precursor and a first oxidant todeposit the super-conformal film 310 within the feature 110. Thesuper-conformal film 310 comprises germanium oxide.

The method for depositing the gap fill material 210 and the method ofdepositing the super-conformal film 310 are similar in several respects.The remainder of the disclosure provides additional details for theseprocesses. Except where clearly identified, the details provided arerelevant to both the deposition of the gap fill material 210 and thesuper-conformal film 310.

For deposition of the gap fill material 210, in some embodiments, thefeature 110 has an opening width in a range of 10 nm to 30 nm, 10 nm to20 nm, 15 nm to 30 nm, 20 nm to 30 nm or 25 nm to 30 nm. In someembodiments, the feature 110 has an aspect ratio (depth divided byopening width) in a range of 2 to 10, 2 to 5, or 5 to 10. In someembodiments, the aspect ratio is in a range of 2.5 to 3.5 or in a rangeof 7.5 to 8.5.

Without being bound by theory, it is believed that the gap fill material210 is marginally flowable and susceptible to capillary forces whendeposited on features with a narrower opening width. The narroweropening increases the likelihood that the gap fill material 210 will bedrawn down, into the feature 110 to form a gap fill material 210 withsubstantially no seams or voids.

For deposition of the super-conformal film 310, in some embodiments, thefeature 110 has an opening width in a range of 50 nm to 200 nm, 80 nm to120 nm, 50 nm to 100 nm, or 100 nm to 200 nm. In some embodiments, thefeature 110 has an aspect ratio (depth divided by opening width) in arange of 2 to 10, 2 to 5, or 5 to 10. In some embodiments, the aspectratio is in a range of 4.5 to 5.5.

In contrast to the gap fill material 210, the super-conformal film 310is typically deposited on features with a relatively wide opening width.This wider width decreases the capillary effect experienced by thesuper-conformal film 310 and allows the super-conformal film 310 toremain on each of the feature surfaces without flowing to the bottom ofthe feature 110.

The substrate 100 or the substrate surface 120 is exposed to the germaneprecursor and the first oxidant simultaneously. In this regard, oneskilled in the art will understand that the germane precursor and thefirst oxidant will react in the gas phase to deposit the gap fillmaterial 210 and/or the super-conformal film 310.

The germane precursor may comprise any suitable compounds for thedeposition of a germanium oxide gap fill material. In some embodiments,the germane precursor comprises one or more of germane (GeH₄) and/ordigermane (Ge₂H₆).

In some embodiments, the germane precursor further comprises hydrogengas (H₂). In some embodiments, the ratio of hydrogen gas to germane isin a range of 5 to 20, 7 to 15 or 8 to 12. In some embodiments, thegermane precursor consists essentially of 10% germane in hydrogen gas.As used in this regard, a process gas which “consists essentially of” astated gas or mixture of gases comprises greater than 95%, greater than98%, greater than 99% or greater than 99.5% of the stated gas or gasseson a molar basis, excluding any inert carrier or diluent gases.

The first oxidant may be any oxygen supplying compound capable ofsupplying oxygen atoms to the germanium oxide gap fill material. In someembodiments, the first oxidant comprises one or more of nitrous oxide(N₂O), oxygen gas (O₂), ozone (O₃) or water (H₂O). In some embodiments,the first oxidant consists essentially of nitrous oxide (N₂O).

In some embodiments, the ratio of the germane precursor and the firstoxidant is controlled. In some embodiments, when depositing the gap fillmaterial 210, the ratio of the first oxidant to the germane precursor isin a range of 5 to 200, 10 to 100, 10 to 50 or 30 to 50. In someembodiments, when depositing the super-conformal film 310, the ratio ofthe first oxidant to the germane precursor is in a range of 50 to 2000,100 to 1000, 100 to 500 or 300 to 500.

In some embodiments, the substrate 100 or the substrate surface 120 isexposed to the first oxidant constantly and the germane precursorintermittently. Stated differently, in some embodiments, the methods arepulsed-CVD type methods where one reactant is flowed constantly and theother is pulsed at a regular interval into the chamber. In someembodiments, the substrate 100 or the substrate surface 120 is exposedto the first oxidant for a period before being exposed to the firstoxidant and the germane precursor simultaneously.

If the germane precursor is flowed intermittently or pulsed, thepercentage of time that the flow of germane precursor is active may bedescribed as the duty cycle. In some embodiments, the duty cycle of thegermane precursor is less than or equal to 50%, less than or equal to33%, less than or equal to 25% or less than or equal to 10%.

The length of the deposition cycle may be any suitable length. In someembodiments, the cycle length is in a range of 10 seconds to 60 seconds,or in a range of 15 seconds to 50 seconds. Accordingly, the length ofthe germane precursor pulse is in a range of 1 second to 30 seconds.

In some embodiments, when the germane precursor is not flowing thesubstrate 100 or the substrate surface 120 is exposed to a secondoxidant. In some embodiments, the first oxidant and the second oxidantare different in composition. In some embodiments, the second oxidantcomprises one or more of nitrous oxide (N₂O), oxygen gas (O₂), ozone(O₃) or water (H₂O). In some embodiments, the first oxidant consistsessentially of nitrous oxide (N₂O) and the second oxidant consistsessentially of oxygen gas (O₂).

In some embodiments, the exposure time for the germane precursor and thesecond oxidant is approximately equal. In some embodiments, the germaneprecursor and the second oxidant are separated by periods ofapproximately the same length. In some embodiments, the substrate isexposed to a deposition cycle comprising a constant flow of the firstoxidant, a germane precursor pulse for 25% of the deposition cycle, afirst pause for 25% of the deposition cycle, a second oxidant pulse for25% of the deposition cycle and a second pause for 25% of the depositioncycle.

In some embodiments, the method of depositing the gap fill material 210is performed without the use of plasma. In some embodiments, the methodof depositing the super-conformal film 310 is performed without the useof plasma. Stated differently, the methods of this disclosure arethermal processes where a plasma-based reactant is not present.

The pressure of the processing environment may also be controlled. Insome embodiments, the methods are performed at a pressure in a range of100 Torr to 500 Torr, in a range of 200 Torr to 500 Torr, in a range of250 Torr to 400 Torr or in a range of 280 Torr to 350 Torr.

The temperature of the substrate 100 may also be controlled. In someembodiments, the substrate 100 is maintained at a temperature in a rangeof 400° C. to 600° C., in a range of 450° C. to 550° C., in a range of400° C. to 500° C. or in a range of 500° C. to 600° C.

The gap fill material 210 and the super-conformal film 310 share somesimilar material properties. In some embodiments, the atomic ratio ofgermanium to oxygen is in a range of 0.2 to 1, in a range of 0.2 to 0.5,in a range of 0.5 to 1, in a range of 0.7 to 1 or in a range of 0.7 to0.9.

Without being bound by theory, it is believed that the use of the secondoxidant, as described above, increases the relative oxygen content ofthe germanium oxide material. Accordingly, the gap fill material 210 orthe super-conformal film 310 deposited by the disclosed methods willhave a relatively low atomic ratio of germanium to oxygen when a secondoxidant is used.

One or more embodiment of the disclosure is directed to methods ofremoving or etching germanium oxide. In some embodiments, the germaniumoxide is removed selectively. As used in this regard, a selectiveremoval process is one in which a target material (e.g., germaniumoxide) is removed more quickly than surrounding material. In someembodiments, the method for removing germanium oxide is selective to oneor more of silicon oxide or silicon nitride. In some embodiments, theselectivity (etch rate of GeOx/etch rate of SiO or SiN) is greater thanor equal to 10, greater than or equal to 20, greater than or equal to 50or greater than or equal to 100.

In some embodiments, the method for removing germanium oxide comprisesexposing germanium oxide to an aqueous solution. In some embodiments,the aqueous solution further comprises hydrogen peroxide (H₂O₂).

In some embodiments, the aqueous solution is acidic. In someembodiments, the aqueous solution comprises sulfuric acid (H₂SO₄). Insome embodiments, the aqueous solution is basic. In some embodiments,the aqueous solution comprises one or more of NaOH or NH₄OH. In someembodiments, the aqueous solution consists essentially of 0.05 M NaOH.

In some embodiments, the aqueous solution is heated to facilitateremoval of the germanium oxide. In some embodiments, the aqueoussolution is heated to a temperature in a range of 60° C. to 100° C., ina range of 70° C. to 90° C., in a range of 65° C. to 75° C. or in arange of 85° C. to 95° C.

Reference throughout this specification to “one embodiment,” “certainembodiments,” “one or more embodiments” or “an embodiment” means that aparticular feature, structure, material, or characteristic described inconnection with the embodiment is included in at least one embodiment ofthe disclosure. Thus, the appearances of the phrases such as “in one ormore embodiments,” “in certain embodiments,” “in one embodiment” or “inan embodiment” in various places throughout this specification are notnecessarily referring to the same embodiment of the disclosure.Furthermore, the particular features, structures, materials, orcharacteristics may be combined in any suitable manner in one or moreembodiments.

Although the disclosure herein has been described with reference toparticular embodiments, those skilled in the art will understand thatthe embodiments described are merely illustrative of the principles andapplications of the present disclosure. It will be apparent to thoseskilled in the art that various modifications and variations can be madeto the method and apparatus of the present disclosure without departingfrom the spirit and scope of the disclosure. Thus, the presentdisclosure can include modifications and variations that are within thescope of the appended claims and their equivalents.

What is claimed is:
 1. A method of selectively removing a gap fillmaterial, the method comprising: depositing a germanium oxide gap fillmaterial in at least one feature on a substrate surface defining asurrounding material comprising silicon oxide or silicon nitride, the atleast one feature having an opening width and extending a depth into thesubstrate; exposing the germanium oxide gap fill material to an aqueoussolution; and selectively removing the germanium oxide more quickly thanthe surrounding material.
 2. The method of claim 1, wherein the openingwidth is in a range of 15 nm to 30 nm.
 3. The method of claim 1, whereina ratio between the depth and the opening width is in a range of 2 to10.
 4. The method of claim 1, wherein the selectively removing thegermanium oxide is selective to the silicon oxide or silicon nitride. 5.The method of claim 4, wherein the selective remove occurs at an etch ofrate of germanium oxide to silicon oxide of greater than or equal to 10.6. The method of claim 4, wherein the selective remove occurs at an etchof rate of germanium oxide to silicon oxide of greater than or equal to20.
 7. The method of claim 4, wherein the selective remove occurs at anetch of rate of germanium oxide to silicon oxide of greater than orequal to
 50. 8. The method of claim 4, wherein the selective removeoccurs at an etch of rate of germanium oxide to silicon oxide of greaterthan or equal to
 100. 9. The method of claim 4, wherein the selectiveremove occurs at an etch of rate of germanium oxide to silicon nitrideof greater than or equal to
 10. 10. The method of claim 4, wherein theselective remove occurs at an etch of rate of germanium oxide to siliconnitride of greater than or equal to
 20. 11. The method of claim 4,wherein the selective remove occurs at an etch of rate of germaniumoxide to silicon nitride of greater than or equal to
 50. 12. The methodof claim 4, wherein the selective remove occurs at an etch of rate ofgermanium oxide to silicon nitride of greater than or equal to
 100. 13.The method of claim 4, wherein the aqueous solution further compriseshydrogen peroxide.
 14. The method of claim 13, wherein the aqueoussolution is acidic.
 15. The method of claim 13, wherein the aqueoussolution comprises sulfuric acid.
 16. The method of claim 13, whereinthe aqueous solution is basic.
 17. The method of claim 16, wherein theaqueous solution comprises one or more of NaOH or NH₄OH.
 18. The methodof claim 4, wherein the aqueous solution is heated to a temperature in arange of 60° C. to 100° C.
 19. The method of claim 18, wherein theaqueous solution is heated to a temperature in a range of 65° C. to 85°C.
 20. The method of claim 18, wherein the aqueous solution is heated toa temperature in a range of 70° C. to 90° C.